LONDON, England (CNN) --Foreign Secretary Jack Straw has defended Britain's decision to include in its first Iraqi dossier claims that Saddam Hussein tried to get uranium from Africa.

Straw Saturday acknowledged that the CIA expressed reservations about the use of the claim in the UK government's September dossier on Iraqi weapons -- but insisted it was based on what British officials regarded as "reliable intelligence" which had not been shared with the United States.

U.S. President George W. Bush said Saturday that he remained confident in CIA director George Tenet after Tenet took responsibility for the line in Bush's State of the Union address alleging that Iraq was trying to buy uranium in Africa -- a line now discredited. (Full story)

In a letter to Donald Anderson, chairman of the House of Commons foreign affairs select committee dated Friday but made public by the UK Foreign Office and shown to CNN Saturday, Straw said: "I am writing to deal with two points relating to the statement in the government's September Iraq dossier that 'Iraq has sought the supply of significant quantities of uranium from Africa.'

"First, press reporting has claimed that this statement is contradicted by the report of a U.S. envoy, Ambassador Joseph Wilson, who visited Niger in early 2002 to investigate the subject on behalf of the CIA.

"I want to make clear that neither I nor, to the best of my knowledge, any UK officials were aware of Ambassador Wilson's visit until reference first appeared in the press, shortly before your hearings last month. In response to our questions, the U.S. authorities have confirmed that Ambassador Wilson's report was not shared with the UK.

"We have now seen a detailed account of Ambassador Wilson's report. It does indeed describe the denials of Niger government officials in early 2002 that a contract had been concluded for the sale of yellowcake (uranium oxide) to Iraq.

"But, as CNN have reported, Ambassador Wilson's report also noted that in 1999 an Iraqi delegation sought the expansion of trade links with Niger -- and that former Niger government officials believed that this was in connection with the procurement of yellowcake.

"Uranium is Niger's main export. In other words, this element of Ambassador Wilson's report supports the statement in the government's dossier.

"Second, the media have reported that the CIA expressed reservations to us about this element of the September dossier. This is correct.

"However, the U.S. comment was unsupported by explanation and UK officials were confident that the dossier's statement was based on reliable intelligence which we had not shared with the U.S. (for good reasons, which I have given your committee in private session). A judgment was therefore made to retain it.

"Finally, may I underline that the JIC's (Joint Intelligence Committee) assessment of Iraq's efforts to reconstitute its nuclear program did not rest on the attempted acquisition of yellowcake alone.

"The government's dossier catalogued a range of other procurement activities, and referred to intelligence that scientists had been recalled to the program in 1998. You will be aware of the recent discovery of technical documentation and centrifuge parts -- necessary for the enrichment of uranium -- buried at the home of an Iraqi nuclear scientist in Baghdad."

In a statement released Friday evening, Tenet said it was a mistake to include in Bush's State of the Union address reports that Iraq was trying to buy uranium oxide. Tenet said that the CIA had seen and approved the president's speech before it was delivered, and he took responsibility for the mistake.

At the time the speech was delivered, Tenet said the line was correct because British intelligence believed that it had evidence of such activity. But he said the CIA's investigation of those same allegations had led the agency to decide that the evidence was inconclusive.

He said: "This is a further blow to the credibility of the British government. It is deeply damaging when allies begin to fall out in public in this way."

Campell and Conservative foreign affairs spokesman Michael Ancram both repeated calls for a full independent inquiry into the war against Iraq.

Campbell added: "Day by day the case for an independent scrutiny of the lead up to the war against Iraq becomes irresistible. Only full disclosure can restore the reputation of this (British PM Tony Blair's) government."